A variety of compactor machines are in widespread use today. Conventional drum compactors, vibratory drum compactors, tamping foot, sheepsfoot, and other lugged or padfoot type compactors are used to prepare work materials for a particular end use. Whether constructing a building, highway, parking lot or compacting landfill trash, it is typically necessary to compact the work material to certain specifications to render it suitable for a particular purpose. Successful compaction of work materials such as soil, gravel, asphalt and even landfill trash may depend upon proper preparation for compaction, as well as certain inherent properties of the work material. In industry parlance, the desired nature of compacted material is generally referred to as a target compaction state.
While achievement of target compaction is often approximated by a density state of the work material, density is not always the desired quantification of quality of a work material. For example, in road construction, the ability of a work material to support a substantial load, i.e. load bearing capacity, is more relevant than a measure of density. Since load bearing capacity is much more difficult to measure, a density specification has been widely accepted in determination of compaction quality. Regardless, deviations from compaction specifications may, at best, result in wasted effort or long work delays, and at worst, can compromise the suitability of the compacted material for an end purpose such as supporting a structure or road traffic.
For example, insufficient compaction can result in unstable support as the work material settles or is penetrated by moisture, causing cracking or buckling in the compacted surface, or insufficient load bearing capacity. On the other hand, overcompaction can deform the work material from its desired condition and can even result in rebound of certain areas of the work material to a less compacted state. The presence of undetected features such as voids, rocks and intrusions of other foreign matter, or inappropriate soil types can have similarly undesirable effects.
Certain undesirable work material conditions may be detected and remedied, but often only by performing the entire compaction procedure again, or by undertaking additional processing steps such as disking the work material or spraying it with water. Other conditions such as the presence of the wrong soil type or mixture have been more difficult or heretofore often impossible to detect. The ability to predict the suitability of work material for compaction, especially for continued compaction once work has started, has thus been recognized as having tremendous potential benefit to the construction industry. It is quite obvious that recognizing compaction problems early, as well as detecting compaction problems typically hidden to an operator, offers the potential of substantially reducing costs and remedial or jobsite downtime, as well as providing for better overall compaction quality assurance.
Engineers have developed a variety of strategies over the years for evaluating compaction state of a work material after treatment with a compactor, or which attempt real time monitoring of compaction state. “Walk out” tests, wherein observation of the penetration depth of toothed wheels of a compactor are in common use. Other tests may require removal of a plug of material from an otherwise finished work surface. More highly sophisticated techniques which do not disturb the work material, such as nuclear gauges, have also been employed with varying degrees of success. While these strategies have improved compaction quality assurance as compared to mere guesswork, they are not without shortcomings.
One method known in the art for improving the efficiency and performance of compaction work is taught in U.S. Pat. No. 6,460,006 to Corcoran (hereafter “Corcoran”), entitled “System For Predicting Compaction Performance”. Corcoran recognizes that compaction performance as determined, for example, from a “compaction response curve,” tends to be relatively predictable for a given combination of a work material condition and compactor type. Corcoran takes advantage of this pattern in predicting a number of compactor passes needed to achieve a target compaction state. Thus, machine passes beyond a point of futility may be avoided by signaling to an operator that additional compactor passes are essentially pointless. The operator may also be alerted in situations where the predicted number of passes indicates that target compaction will likely never be achieved due to excessive moisture content, etc. While Corcoran provides a useful insight regarding work material compaction data under certain conditions, there remains room for improvement. In particular, Corcoran is most applicable where the compacted work material follows a relatively predictable compaction response. It is desirable, however, to also evaluate compaction suitability in instances where the compaction response is not necessarily well behaved. In essence, Corcoran is useful for determination that a problem exists, but does not provide an analysis of the problem.
The present disclosure is directed to one or more of the shortcomings or problems set forth above.